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Explanation:
Use the remote interior angle theorem. This says to add the interior angles shown, and you'll get the exterior angle that is not adjacent to those interior angles.
68+65 = 133
So angle B is 133 degrees
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A longer alternative is to let C be the missing interior angle of the triangle. Then we can find that
68+65+C = 180
C+133 = 180
C = 180-133
C = 47
Angle C is adjacent to the exterior angle B, meaning
B+C = 180
B+47 = 180
B = 180-47
B = 133
